ndisgen does give a few problems because it is far stricter than Windows' parser for .INF files.
Can you post your the offending line here (or perhaps the whole INF file) so that we can see what's wrong?
Here are a few things that may trip up ndiscvt:
1) DOS/WIN eol characters (CRLF or \r\n vs \n for *nixes). If you open up the INF file in vi you will probably see ^M at the end of every line. To fix this quickly, open up your file, then press the following sequence exactly (I am assuming you don't know vi
if you do, then awesome!
). Oh yeah the [CTRL+V] and the [CTRL+M] means you should press ctrl and v and ctrl and m.
First hit ESC, then:
When you type, that it should appear like this in the bottom:
This will remove all the ^M characters in the file. After that, type ":wq" to save the file. Try ndisgen again.
2) Weird characters. For example, some INF files have support for different languages and may use characters that have accents on them. ndiscvt chokes on these sometimes.
3) Syntax errors. Some times parentheses aren't closed, or there are just blatant syntax errors. See if you can fix them.
Anyway, hope this helps. Post your file here if you can so we can take a look at it.